The following relates generally to wireless communication, and more specifically to techniques for enhanced broadband operation of an active mixer.
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system, or a New Radio (NR) system). A wireless multiple-access communications system may include a number of base stations or access network nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
Wireless communication devices, such as a UE or base station, include one or more mixers. A mixer is a non-linear circuit that may be used to shift a signal from one frequency to another for transmission or signal processing. A mixer is a 3-port electronic circuit, where two of the ports are “input” ports and the other port is an “output” port. The mixer mixes the two input signals such that a frequency of the output signal is either the sum (or difference) of the frequencies of the input signals. A mixer may be used to upconvert signals to radio frequencies for transmission, and downconvert received signals from radio frequencies to lower frequencies for processing. Two types of mixers are passive mixers and active mixers. A passive mixer may use diodes and rely on the non-linear relation between voltage and current to generate the mixer output. In a passive mixer, however, the output signal is of lower power than the input signals. An active mixer may use an amplifying device (such as a transistor or vacuum tube) to increase the strength of the output signal. However, operating at high frequencies such as millimeter wave (mm-wave) frequencies constrains the type of mixer that can be used. Generating a square-wave local oscillator (LO) signal having a high-swing to drive a passive mixer is prohibitively power-hungry at mm-wave frequencies. In many instances, only an active mixer can tolerate a low-swing sinusoidal LO signal waveform and provide acceptable performance. As wireless communication techniques improve, conventional mixers do not provide adequate performance.